In recent years, as semiconductor devices have been miniaturized, internal wirings in these devices have also been miniaturized. As the wirings have become smaller, a narrow line effect in which scattering effects caused by interfacial and grain boundaries in copper wirings of the related art begins to predominate, and wiring resistance consequently increases appreciably.
For this reason, wirings in the semiconductor devices according to the related art often fail to satisfy device specifications and/or meet performance targets. Therefore, it is preferable to use a material which is hardly affected by narrow line effects. However, since materials in which narrow line effects are hardly apparent generally have a high bulk specific resistance, when the same material is used for a wide wiring as used for narrow wiring, the wide wiring will have a high resistance and overall device performance may not be substantially improved.